Objective Under noninvasive positive pressure ventilation, in view of inconvenient operations in human airway, and avoiding the interference of spontaneous breathing and the necessary leakage flow, the method for dynamic online monitoring of the respiratory resistance (R) and compliance (C) was studied.Methods At the end of expiration, when the exhaled flow was 0, relative to the expiration positive airway pressure (EPAP), a step-dropped pressure was produced with the amplitude Δp and hold time Δt. Under this dropped pressure, a short-time discharged flow was generated from the lung, and the discharged flow was applied to calculate the R and C. In addition, a respiratory model was developed in MATLAB to simulate the breaths of normal adult, acute respiratory distress syndrome (ARDS) patient and chronic obstructive pulmonary disease (COPD) patient. A serial of simulation experiments were carried out for obtaining data and verification.Results The calculated R and C from simulation for normal adult, ARDS patient, COPD patient, deviated from the actual value by 1.60% and -1.60%, 1.21% and -1.19%, -12.53% and 14.32%, respectively.Conclusions The proposed algorithm is practicable and feasible for calculating the R and C. The simulation results are beneficial for studying and realizing the intelligent ventilation and proportional assist ventilation in respirator.

Objective T o analyze the influence of high flow nasal cannula (HFNC) on trespiratory mechanical parameters of the patient with acute respiratory distress syndrome (ARDS) based on ventilation experiment, and investigate the therapeutic and side effects of the HFNC. Methods The HFNC ventilation system model based on MATLAB and the physical experiment platform based on active simulated lung ASL5000 were developed to simulate the respiratory movement of ARDS patients with different lung compliance, and a series of the HFNC ventilation experiments were carried out. Both experimental results in MATLAB and physical platform were compared and analyzed. Results The results from the Matlab model-based simulation experiment and physical platform based-physical experiment uniformly showed that increasing the output flow of HFNC would decrease the relevant respiratory mechanical parameters of respiratory flow and tidal volume, but increase the intrapulmonary pressure and the functional residual capacity (FRC). Under the condition of small flow, the output flow from HFNC might be smaller than the inspiratory flow required by the patient, and an inspiratory compensation flow was necessary to make up for the inspiratory flow. Conclusions The necessary reliable compensation flow in inspiration will promote the security of HFNC. Understanding the changes in respiratory mechanical parameters of ARDS patient will be beneficial to pre-evaluate the HFNC, improve the ventilation effect and reduce the ventilation risks.

Without artificial airway though oral, nasal or airway incision, the bi-level positive airway pressure (Bi-PAP) has been widely employed for respiratory patients. In an effort to investigate the therapeutic effects and measures for the respiratory patients under the noninvasive Bi-PAP ventilation, a therapy system model was designed for virtual ventilation experiments. In this system model, it includes a sub-model of noninvasive Bi-PAP respirator, a sub-model of respiratory patient, and a sub-model of the breath circuit and mask. And based on the Matlab Simulink, a simulation platform for the noninvasive Bi-PAP therapy system was developed to conduct the virtual experiments in simulated respiratory patient with no spontaneous breathing (NSB), chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS). The simulated outputs such as the respiratory flows, pressures, volumes, etc, were collected and compared to the outputs which were obtained in the physical experiments with the active servo lung. By statistically analyzed with SPSS, the results demonstrated that there was no significant difference ( P > 0.1) and was in high similarity ( R > 0.7) between the data collected in simulations and physical experiments. The therapy system model of noninvasive Bi-PAP is probably applied for simulating the practical clinical experiment, and maybe conveniently applied to study the technology of noninvasive Bi-PAP for clinicians.
Humans ; Respiration, Artificial/methods* ; Positive-Pressure Respiration/methods* ; Respiration ; Ventilators, Mechanical ; Lung